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PDBsum entry 2g0f
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Oxidoreductase
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PDB id
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2g0f
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References listed in PDB file
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Key reference
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Title
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Crystal structures of e. Coli ccmg and its mutants reveal key roles of the n-Terminal beta-Sheet and the fingerprint region.
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Authors
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N.Ouyang,
Y.G.Gao,
H.Y.Hu,
Z.X.Xia.
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Ref.
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Proteins, 2006,
65,
1021-1031.
[DOI no: ]
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PubMed id
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Abstract
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CcmG, also designated DsbE, functions as a periplasmic protein thiol:disulfide
oxidoreductase and is required for cytochrome c maturation. Here we report the
crystal structures of Escherichia coli CcmG and its two mutants, P144A and the
N-terminal fifty seven-residue deletion mutant, and two additional deletion
mutants were studied by circular dichroism. Structural comparison of E. coli
CcmG with its deletion mutants reveals that the N-terminal beta-sheet is
essential for maintaining the folding topology and consequently maintaining the
active-site structure of CcmG. Pro144 and Glu145 are key residues of the
fingerprint region of CcmG. Pro144 is in cis-configuration, and it makes van der
Waals interactions with the active-site disulfide Cys80-Cys83 and forms a
C--H...O hydrogen bond with Thr82, helping stabilize the active-site structure.
Glu145 forms a salt-bridge and hydrogen-bond network with other residues of the
fingerprint region and with Arg158, further stabilizing the active-site
structure. The cis-configuration of Pro144 makes the backbone nitrogen and
oxygen of Ala143 exposed to solvent, favorable for interacting with binding
partners. The key role of cis-Pro144 is verified by the P144A mutant, which
contains trans-Ala144 and displays redox property changes. Structural comparison
of E. coli CcmG with the recently reported structure of CcmG in complex with the
N-terminal domain of DsbD reveals that Tyr141 undergoes conformational changes
upon binding DsbD. A cis-proline located at the N-terminus of the first
beta-strand of the betabetaalpha motif of the thioredoxin-like domain is a
conserved structural feature of the thioredoxin superfamily.
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Figure 5.
Figure 5. The active-site disulfide and the cis-proline loop of
CcmG-EC in comparison with those of the P144A mutant and of DsbC
in the DsbC-nDsbD complex. CcmG-EC is shown in red in the left
panel, P144A in green in the central panel, DsbC in pink in the
right pannel (the side-chain of Y100 in green for clarity), and
nDsbD in blue in the three panels. The C  H
 O
hydrogen bond and interprotein hydrogen bonds are shown as
dotted lines. This diagram was prepared using the program SETOR.
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Figure 6.
Figure 6. Redox equilibrium of CcmG-EC (squares) and the P144A
mutant (circles) with glutathione.
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The above figures are
reprinted
by permission from John Wiley & Sons, Inc.:
Proteins
(2006,
65,
1021-1031)
copyright 2006.
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